1. Field of the Invention
This invention relates to a method and apparatus for transportation of materials, in which materials to be machined by individual machine tools are continuously circulated on a conveyor, and a specific one selected from among them is unloaded from the conveyor to be supplied to a specific machine tool when the specific material is requested by the specific machine tool.
2. Description of the Prior Art
Hitherto, materials to be machined by individual machine tools according to the production schedule have been previously distributed to corresponding ones of the machine tools, or such materials have been stored in a warehouse so that a specific one selected from them can be supplied by a conveyor from the warehouse to a specific machine tool upon request for machining by the machine tool. However, the former method is not applicable to a production system in which the production schedule is frequently changed resulting in a corresponding change of the machine tools participating in material processing or the production schedule cannot be sufficiently laid out in advance. According to the latter method, on the other hand, pallets on which the materials are carried, respectively, are marked by a central unit according to the production schedule with the addresses of specific machine tools which are scheduled to process the materials and the pallets are transported by the conveyor. Thus, in the case of the latter method, the relationship between the machine tools and the materials to be processed thereby must be preliminarily determined. Further, an addressing error of the central unit results in maloperation of the whole system. Further, it has been required for the central unit to collect and process a vast amount of information, since the central unit must always exactly grasp the operating state and occurrence of operational failure, if any, of the individual machine tools. Furthermore, the latter method, in which a material is not transported to a machine tool by the conveyor until the machine tool requests distribution of such a material, has been defective in that a considerably long period of time is required until the material is actually supplied to the machine tool after the request is issued.